Geography Reference
In-Depth Information
On the other hand, for urban dynamic structure analysis, phone call activi-
ties and phone users' physical movement flows were aggregated based on the
Voronoi polygons.
More detailed spatio-temporal analysis and results will be presented in the
following section.
4. E XPERIMENTS
4.1. Individual Spatial-Temporal Movement Patterns
In urban studies, the understanding of human movement patterns over
time is very important in transportation planning and city management. Figure
5 illustrates the 3D STV of a person's mobile tracking trajectories in space
over one-week. Each color represents a single mobile subscriber. Different
shapes of 3D polylines reveal different space-time behaviors for specified
users. For instance, the regular patterns at fixed locations (e.g. home and job
places) with respect to the daily/weekly cycles can be indicated by the length
of vertical segments of the space-time paths (Figure 5a). In addition, irregular
movement patterns have been also found for certain type of individuals
(Figure 5b). One might guess that the user is a delivery employee or working
for related professions. The STV technique can help to simultaneously
visualize the mobile trajectory patterns in space and time with an intuitive
manner but may need the statistical analysis to extract more meaningful
personal places of interests (POIs). Figure 6a displays the spatial distribution
of a mobile user's call-activity movement in a week. It tells that this person
has a higher probability (Cell A: 0.31, Cell B: 0.22; Cell C: 0. 14) to
frequently visit a few places, while the visiting probability of most cells is less
than 0.05). The interpretation of the time series graphs of these frequently
visited places by the user offers the possibility to identify the personal POIs.
As shown in Figure 6b, the user often made phone-calls at Cell A and Cell B
during 19:00~24:00 throughout the whole week.
One can infer that his/her home might locate nearby or inside the
boundary of the two cells. Also, the temporal signature of Cell C may indicate
a working place since the user present there only during office hours
(9:00~18:00) on weekdays and not on weekends. However, the detailed
information about personal characterized POIs may need more investigation
on daily-activity trips of the mobile subscribers or the study of geographical
contexts.
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